Maximizing the recovery of petroleum from marginally productive domestic oil fields is important to U.S. energy independence goals and national security interests. However, in order to be competitive with imported petroleum, the domestic petroleum must be recovered in a cost efficient manner in order to be commercially viable. Traditionally, techniques for the pumping of petroleum involved either continuously operating a pump unit or controlling the pumping unit with a simple electromechanical timer to avoid peak electrical energy charges. Neither of these techniques is suitable for optimizing the extraction of petroleum from marginally productive oil fields.
Furthermore, these techniques waste electrical energy and cause excessive wear and tear on the pumping equipment, thus increasing operational and maintenance costs which decreases the economic viability of the operation. As a result, marginally productive oil fields are often underutilized due to the high electrical energy costs incurred and resulting low production yields resulting from the production wells.
In order to efficiently extract petroleum from these marginal oil fields, a system should be employed which detects when a pumping system encounters an abnormal pumping situation. For example, a commonly encountered abnormal pumping situation is known as “fluid pound”.
Fluid pound occurs when the drawing well is pumped-off, i.e., when petroleum is extracted from a well at a rate greater than the rate at which the petroleum is recharged by the petroleum bearing formation. In a pump-off situation, a working well is only partially filled during an upstroke of a plunger. Upon the plunger's downstroke, the plunger strikes or “pounds” the remaining fluid in the working well causing severe jarring of the entire pumping unit which may lead to damage of the pumping unit and decreased pumping efficiency.
Many solutions are known in the relevant art to address the pump-off situations in a petroleum production environment. For example, several references teach measuring changes in the load on a reciprocating member associated with a downhole pump; U.S. Pat. No. 3,838,597 to Montgomery, et al.; U.S. Pat. No. 4,286,925 to Standish; U.S. Pat. No. 5,044,888 to Hester; U.S. Pat. No. 6,155,347 to Mills; measuring current and voltage phase relationships associated with an electrical driving motor U.S. Pat. No. 5,362,206 to Westerman, et al.; measuring the instantaneous rate of both pulsating and steady-state flow; U.S. Pat. No. 5,006,044 to Walker et al.; measuring vibrations incident on reciprocating member associated with a downhole pump, SPE 62865, “Marginal Expense Oil Well Wireless Monitoring,” D.Nelson, H.Trust, Society of Petroleum Engineers, 2000; sonically measuring pump-off, U.S. Pat. No. 4,171,185 to Duke, et al.; and expensive hybrid computer controlled systems monitoring a plurality of pump operating parameters, U.S. Pat. No. 5,941,305 to Thrasher, et al.
Although many of these solutions may be effective, these solutions tend to have one or more disadvantages including requiring expensive monitoring equipment, requiring frequent calibration and/or requiring frequent maintenance in the corrosive and toxic environment of marginally productive petroleum fields. As such, the added incremental costs of providing one or more of these solutions generally limit their application to larger and more productive fields. Smaller and marginally productive fields necessarily require low cost and low maintenance solutions in order to be economically viable.
Therefore, it would be highly advantageous to provide a simple, low cost monitoring and control system which maximizes recovery of petroleum, minimizes energy usage and requires minimal ongoing maintenance.